1. Field of the Invention
The present invention relates to a new and improved suction roll, especially for a paper web drier of a papermaking machine.
Generally speaking, the suction roll of the present development, especially for use in a paper web drier of a papermaking machine, is of the type comprising a perforated roll shell or jacket having an inner surface or wall. Within this perforated roll shell there is located an internal chamber or space divided by a wall member which is transversely arranged with respect to the lengthwise axis of the suction roll. The suction roll also has a connection or connection means flow communicating or connecting the internal chamber with a suction device, preferably a vacuum pump. At least one blade or vane which extends transversely with respect to the inner surface of the roll shell is arranged in the internal chamber.
2. Discussion of the Background and Material Information
Such type equipment is known in the papermaking art from, for example, U.S. Pat. No. 4,876,803, granted Oct. 31, 1989. The suction roll constructions disclosed therein are considered to be afflicted with the appreciable drawback that there are required large pressure differentials, and thus, also large vacuum pumps. Due to the air flows occurring internally of the suction roll there arises a pressure drop, and frequently there is no longer present an adequate pressure differential in order to retain the paper web at the suction roll.
Additional constructions of suction rolls have been taught, for example, in European Published Patent Application No. 0,413,671, published Feb. 20, 1991. In this case, a disk is arranged at the end of the suction roll at the neighborhood of the suction action which takes place through a shaft of the suction roll. This disk is fixedly connected by individual webs or struts with a cover of the suction roll, and thus, co-rotates with the suction roll. Also these suction roll constructions are only capable of reducing cyclone-type or rotary flow conditions to a limited extent.